Rarely can one safely say from a purely aural knowledge of a single performance that any new work is a masterpiece. But at last such an opportunity has come with the Zorian's performance of Tippett's third Quartet. Beside it, many fine quartets of this century are dwarfed, and Bartók's alone seem of comparable stature. There is indeed a strong resemblance to Bartók's fifth Quartet. In both works the composers are most accessible, yet most individual; both achieve amazing textural clarity in combination with exquisite new sonorities; lastly, both quartets have five movements, alternately fast and slow, of approximately corresponding character. There is in each work a profound first movement, a jaunty high-speed, folkish third, (Tippett's containing bagpipe effects similar to those in certain movements of Bartók marked Cornemuse) and a puzzling fifth, problematical because it presents no problems, which makes us unsure how to interpret it. Not that these two movements have anything else in common except that they are fine music. Bartók's is a wry sneer at the eighteenth-century rondo, Tippett's a gentle epilogue, but just as the sneer is out of place and puzzling in the one very serious quartet, so is the ingenuousness of the epilogue in the other.